Location-determining systems may comprise location-determining receivers (e.g., Global Positioning System receivers) that receive signals from satellite beacons to estimate the location of a vehicle. However, terrain, buildings, vegetation, or other natural or man-made obstructions may reduce the signal strength and reliability of the received signals, hence, the accuracy of location estimates of the vehicle. Thus, there is a need to augment or enhance the location-determining capability of the location-determining receiver to improve accuracy or reliability of location estimates of the vehicle.